This invention is directed to an economical but efficient system for releasably fastening articles of apparel. Since it is particularly concerned with those articles generally known as disposable diapers, reference will be made thereto for purposes of illustration in the following description.
Typically, disposable diapers comprise a porous absorbent material for placement against the body and an outer liquid-impermeable liner. Obviously, means must be provided for releasably securing the diaper on the body.
The evolution of diaper closure systems has progressed through several stages from pins through permanently positioned tapes; movable tapes with the attachment area on the diaper specially reinforced to prevent tearing; then to movable tapes having a thicker attachment area with a roughened surface intended to decrease adhesion and, in turn, to prevent tearing; and finally to the so-called "repositionable tapes" currently employed on virtually all of the disposable diapers now on the market. These repositionable tapes generally are in the form of a tab engaging opposed edges adjacent one end of the diaper and adapted for releasably securing the plastic liner on the opposed end when the two ends are brought in superposition to cover the front and back lower region of the corpus.
As will be described in more detail hereinafter, these adhesive tabs are usually composed of two sheet materials, each carrying an adhesive surface. The adhesive layer on the first of these sheet materials is adapted for permanently securing this sheet material and an underlying portion of the second sheet material to the inner surface of the diaper. The second of these sheet materials is hinged with a portion underlying the first sheet material. As mentioned, the exposed portion carrying a less tacky or adherent adhesive layer is adapted for releasably engaging the plastic liner on the opposed end of the diaper when brought into superposition. Prior to use, the adhesive layer on the second sheet material may be hinged or folded into contact with the non-adhesive surface of the first sheet material, which surface then functions as a release liner protecting the repositionable adhesive layer. To facilitate this release function, the contact area on the backing of the first sheet material may contain a coating of silicone or other suitable material providing the release function. In use, the repositionable adhesive is simply peeled away from the first sheet to provide the adhesive tab for securing the diaper.
As will be appreciated, diaper closure systems such as the aforementioned repositionable tapes must possess certain criteria for optimum efficiency. On the one hand, they must possess the requisite peel adhesion, shear strength, and stability on aging to secure the diaper. On the other hand, this adhesion must not be so great as to tear the plastic liner when the tape is peeled therefrom. In essence, the adhesive must adequately secure the diaper while at the same time being alternately releasable and re-attachable a plurality of times without tearing the attachment area of the plastic liner.
Throughout the evolution of diaper closure systems from safety pins and the like, this tearing of the plastic attachment area has remained a constant problem, even though it may occur in only a small number of cases. In fact it is still regarded as the singlemost problem in the disposable diaper industry today. Consequently a "full proof" closure system is still needed.
In an effort to satisfy this need, various alternatives to the current tape systems have heretofore been considered. For example, U.S. Pat. No. 3,840,013 discloses a disposable diaper employing Velcro fasteners. However, its manufacturing costs are too great to be considered as a viable substitute.
The present invention is directed to the aforementioned problem of providing a releasable or repositionable closure system which will severely limit if not entirely preclude incidents of tearing, which closure system is both elegant and compatible with the existing diaper-making machines.